The basic measurement of electrical power depends on voltage, current and time, all of which are relatively simple to measure, using basic devices such as a voltmeter, ammeter and clock, or a multimeter. A power supply, however, has many more features, all of which influence the nature and quality of the supply, including wave-form, phase/phase shift and harmonics. Power test instruments can provide in-depth measurement, analysis and recording of all relevant data and have a wide range of uses, from simply monitoring domestic electricity usage to checking the quality of electrical power-producing equipment. Power test instruments are available for single and three-phase supplies and may be used to identify inefficiencies and waste, or possibly to examine the nature of the supply during a motor start-up. Checking waveform features such as TRMS can, of course, be done using an oscilloscope, but advanced power analysers have greater powers of analysis and data-logging capabilities, along with extensive connectivity options. On a much simpler scale, some basic instruments may simply need plugging into a power socket.